The present invention concerns a kneader, and more specifically a kneader capable of eliminating a cleaning process in the kneading process, by preventing gushing of the filler through the clearance between the mixing tank and the pressurizing lid, stabilizing the blending ratio of the filler and preventing defective dispersion due to fall and mixing of the filler after the completion of kneading, for promoting improvement of dispersion and uniformity of kneaded materials such as rubber, plastics, etc. as well as stability of quality.
Conventionally, a kneader is constructed by disposing a pair of rotors, 2 in a mixing tank 1 as shown in FIG. 11, in a way to turn inward mutually, forming a rotor blade 22 (twisted blade) by twisting the rotor so that the kneaded material may constantly be forwarded to the inner side (center side) of the mixing tank 1, and further disposing a pressurizing lid 4 at the top of the mixing tank 1, to have the kneaded material such as rubber, plastics, etc. bitten by the pair of rotors, 2.
Moreover, to perform the biting of kneaded material between the rotors more effectively, the kneader is constructed by disposing a pressurizing means such as an air cylinder, etc. (not illustrated) on the pressurizing lid 4 to enable to move the pressurizing lid 4 up and down in a state in which a certain pressurizing force is applied to it, so that the inner section of the mixing tank 1 may have a shape and an inner volume suitable for the kneaded material.
By the way, when kneading the kneaded materials by using this type of kneader, there are cases where the volume and shape of the voids in the kneaded material change in a variety of ways with the rotation of the rotors, 2, and the reactional force of the material behavior due to this change causes dancing of the pressurizing lid 4, eventually making the filler contained in the kneaded materials gush out through the clearance between the mixing tank 1 and the pressurizing lid 4 together with air.
And, it was a normal practice to mount a dust cover at the point of the mixing tank 1 where the filler gushes out, to prevent the gushed filler from flying to the surrounding area and to also facilitate cleaning of the gushed filler and, when the area around the top part of the mixing tank 1 and the top face of the pressurizing lid 4 are stained with the gushed filler, clean up the filler by opening the dust cover.
However, if the filler gushes out to the top part of the pressurizing lid 4, it not only stains the surrounding area but also presents a problem of remarkably lowering the productivity, because it becomes necessary to set a cleaning process of the filler which accumulated at the top face 42 of the pressurizing lid 4 and at the peripheral part 1a of the opening at the top of the mixing tank 1 in the kneading process, and stop the equipment operation for it.
Moreover, another problem was that a change of blending ratio is produced in proportion to the spouted filler, causing unevenness of quality among batches, or the filler which accumulated at the top face 42 of the pressurizing lid and at the peripheral part 1a of opening at the top of the mixing tank drops and is mixed in the material at the time of discharge of the material after the completion of kneading, causing a defective dispersion, etc. (see Laid-Open Patent Publication No. H7-61438, for example).